There is much evidence to suggest that the extent of carcinogen-induced promutagenic DNA damage and the capacity of cells to repair such damage represent critical events in the initiation of carcinogenesis. We are studying the in vivo formation and repair of benzo(a)pyrene metabolite-DNA adducts in target and non-target organs for benzo(a)pyrene-induced neoplasia. The effect of benzo(a)pyrene metabolite-DNA adducts on de novo synthesis is being investigated. We are concerned with the effect of dose of BP and inhibitors of benzo(a)pyrene-induced carcinogenesis on the amount and type of adducts formed. Emphasis is on studies which enhance our understanding of the relationship between metabolism of BP and the amount and types of DNA adducts formed in the various tissues.